1. Field of the Invention
The present invention relates to a prothesis for a natural human heart that may be used for the surgical correction of a deformed heart valve. In particular, the present invention relates to a holder for a flexible annuloplasty ring prosthesis for use in properly positioning the annuloplasty ring about the valve annulus during implantation.
2. Description of the Related Art
The human heart includes four valves, each comprised of several cusps, that control the flow of blood through the heart. The geometry of these valves is important in their function. More particularly, the geometry helps ensure cusps of the valve overlay each other to assist in controlling the regurgitation of the blood during ventricular contraction. Diseases and certain natural defects to heart valves can impair the functioning of the cusps in preventing regurgitation. For example, certain diseases dilate the heart valve annulus. Dilation may also deform the valve geometry or shape, thereby displacing one or more of the valve cusps from the center of the valve. Other diseases or natural heart valve defects result in deformation of the valve annulus with little or no dilation.
Various surgical procedures have been developed to correct deformations of the valve annulus and retain the intact natural heart valve. These surgical techniques involve repairing the shape of the dilated or elongated valve. Such techniques, generally known as xe2x80x9cannuloplasty,xe2x80x9d require surgically restricting the valve annulus to minimize dilation. Typically, a prosthesis known as an xe2x80x9cannuloplasty ringxe2x80x9d is sutured around the base of the valve leaflets. The annuloplasty ring reshapes the valve annulus and restricts the movement of the valve annulus during the opening and closing of the valve.
Initially, the annuplasty rings were designed as rigid frame members, to correct the dilation and reshape the valve annulus to the natural state. This type of annuloplasty ring is referred to as xe2x80x9crigid,xe2x80x9d and they are still in use today. Rigid annuloplasty rings are formed from a metallic or other rigid material that flexes very little, if at all, during the normal valve operation. Rigid annuloplasty rings adequately promote proper valve performance by restricting valve dilation and reshaping the valve annulus. However, their rigidity prevents the normal flexibility of the valve annulus and may contribute to left ventricular outflow tract obstruction. Another disadvantage with a highly rigid annuloplasty ring is the tendency of the sutures to tear during the normal movement of the valve annulus.
Some in the art have therefore suggested using completely flexible annuloplasty rings. Flexible annuloplasty rings typically include an inner support formed from a flexible material. This support is wrapped in a woven, biocompatible cloth material. Resistance to the dilation of the annulus during the opening and closing of the valve is obtained by properly suturing the ring about the valve annulus. One disadvantage with completely flexible annuloplasty rings is that, during the implantation process, the ring may become bunched at localized areas. This bunching results in the phenomenon known as multiple plications of the annuloplasty ring. One consequence of this phenomenon is variability of the ability of the ring to control the shape of the valve annulus. The bunched areas of the ring tend to provide a more rigid area in comparison to the other portions of the ring, which distorts the valve annulus during valve operation.
One approach sutures the annuloplasty ring to a rigid plastic holder that maintains the ring in its proper shape during the procedure. The holder is in turn releasably secured to a bendable handle that can be formed by the surgeon to facilitate positioning of the ring and holder in the heart concentrically and coplanarly with the annulus of the valve to be repaired. Once the holder is placed and sutures initiated, the handle is withdrawn to give the surgeon room to work and properly see the annulus. When the procedure is completed, valve closure is tested by injecting saline solution. The sutures attaching the ring to the holder are then cut, and the handle and holder are removed, leaving the ring in place.
A problem arises in the release and reattachment of the handle. Because the handle is bent, and because rotary stress on the holder and ring is undesirable, rotary movement (and, for that matter, axial movement also) of the handle during release and attachment must be minimized. The prior art has attempted to deal with this problem in various ways. For example, U.S. Pat. Nos. 5,041,130 and 5,350,420 to Cosgrove et al. disclose a releasable interlock using a pin and J-shaped slot which is released and engaged with a partially rotary, partially axial movement of the handle, while Baxter International, Inc.""s Model 4450 uses an axially engageable (but non-releasable) interlock.
The present invention is directed to resolving one or all of the problems mentioned above.
The invention, in a first aspect, is an apparatus for holding a flexible annuloplasty ring during implantation. The apparatus comprises a top piece including a bottom surface sized to engage substantially all of the inner diameter of the annuloplasty ring and finished to grip the annuloplasty ring; a bottom piece including a top surface sized to engage substantially all of the inner diameter of the annuloplasty ring and finished to grip the annuloplasty ring; and a haft capable of engaging the top and bottom pieces to releasably clamp the annuloplasty ring therebetween.
In a second aspect, the invention is a method of manipulating a flexible annuloplasty ring for implantation. The method comprises disposing the annuloplasty ring between a top piece and a bottom piece; and engaging the top piece and the bottom piece with a haft to releasably clamp the annuloplasty ring between the top and bottom pieces.